Instruments for minimally invasive surgery total knee arthroplasty

ABSTRACT

An anti-backout stylus comprising a stylus and a locking stylus holder. The locking stylus holder engages the stylus at a series of discrete positions during insertion of the stylus into the holder. The locking stylus holder prevents inadvertent backing out of the stylus by preventing the stylus from being withdrawn to a previous one of the discrete positions. The locking stylus holder can preferably be selectively disengaged from the stylus to allow for selective withdrawal of the stylus. Each engagement of one of the discrete positions by the locking stylus holder preferably indicates a femoral size. The discrete positions are preferably defined by detents formed on the stylus and a stop member on the locking stylus holder. The locking stylus holder can be provided on an anterior rough cut guide, with the anterior rough cut guide preferably mountable on an intramedullary rod.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, claims priority to andincorporates by reference U.S. patent application Ser. No. 13/969,024filed Aug. 16, 2013, now U.S. Pat. No. 8,998,908, U.S. patentapplication Ser. No. 11/358,899, filed Feb. 21, 2006, now U.S. Pat. No.8,734,453, Provisional Patent Application Ser. No. 60/654,441, filedFeb. 21, 2005 and Provisional Patent Application Ser. No. 60/723,092,filed Oct. 3, 2005.

FIELD OF THE INVENTION

The present invention relates to orthopedic surgery, and moreparticularly to instruments for use in minimally invasive total kneearthroplasty.

BACKGROUND OF THE INVENTION

Total knee implants have been around for many years. Over the years,various instruments have been developed for preparing the distal femurand the proximal tibia for receipt of knee implants. In recent years,efforts have been made to minimize the length of the incision byapplying “minimally invasive surgery” (“MIS”) techniques to total kneearthroplasty (“TKA”) procedures. MIS TKA procedures minimize trauma totissues and reduce patient recovery time. MIS TKA procedures attempt touse the smallest incision possible. However, the length of the incisionis constrained by several factors, including the size of the implant,the size and type of instruments used to resect the knee, the necessityof making accurate recisions, the need to minimize trauma to the skin inthe area around the incision, and the skill and experience level of thesurgeon. The present application is directed to MIS TKA instruments thatare particularly adapted for making accurate femoral resections withinthe confined spaces encountered in MIS TKA procedures. The instrumentsminimize damage to the skin and assist both experienced and lessexperienced surgeons in successfully carrying out MIS TKA procedures.

The following background material is incorporated from applicant'sco-pending U.S. patent application Ser. No. 10/794,188 (Publication No.2005/0209600), which is incorporated herein by reference. Performance ofa knee replacement surgery typically includes modification of one, orboth, of the proximal end of the tibia and the distal end of the femurto have a shape that accommodates the tibial and femoral components,respectively, of the knee prosthesis. Modification typically involvessome type of cutting procedure, e.g., with a bone saw, to prepare planarsurfaces on the femur for attachment of the femoral component. Aneffective attachment of the femoral component to the femur isfacilitated by cutting the femur at appropriate depths and angles thatmatch the dimensions and angles of the attachment (i.e.,non-articulating) surfaces on the underside of the femoral component.

The femur, due to its complex geometry (e.g., lateral and medialcondyles and intracondylar notch) can be particularly difficult to shapeand therefore benefits greatly from accurate cuts. In addition, propersizing of the components is important to ensure that the knee prosthesishas adequate stability and range of motion. To this end, variouscalipers and resection guides have been developed that measure the tibiaand femur to determine appropriate sizes for the femoral and tibialcomponents.

The ADVANCE® brand single reference point knee replacement system(Wright Medical, Inc., Arlington, Tenn.) includes a femoral caliper thatworks off of a single reference point to size the femoral component. Theknee replacement system also includes a guide for guiding subsequentcuts to the femur. During femur preparation, first, a starter hole isinitiated in the femoral (medullary) canal between the condyles using adrill bit. A fluted intramedullary reamer is inserted into the femoralcanal and is turned by hand by grasping and twisting a T-handle endattachment to reduce the occurrence of fat embolisms. An intramedullaryalignment rod is then inserted into the reamed hole, preferably at avalgus angle of about 3° or 5°, and becomes the single point from whichthe remaining cuts are referenced.

A distal femoral resection guide is then assembled onto theintramedullary rod and is placed against the most prominent distalfemoral condyle. The resection guide includes slots that are sized tosupport a bone saw (or other) blade as it cuts a section of the distalfemur to form a flat surface in a “distal rough cut.” After the initialcut, the distal surface can then be gently planed until flat by a planerthat is rotated about the intramedullary rod. The preferred amount ofdistal resection is between 9 mm and 13 mm.

After planing, the femoral sizing caliper is placed over theintramedullary rod and against the flat, resected distal femur. A pairof feet of the femoral sizing caliper are placed adjacent the posteriorportion of the medial and lateral femoral condyles, while a feeler gaugeis placed in contact with the anterior cortex of the femur. Movement ofthe feeler gauge and the feet into position registers a size on a sizingguide of the femoral sizing caliper.

Once the component size has been determined, an anterior-posteriorresection guide corresponding to the previously measured size of thefemoral component is placed over the intramedullary rod. Theanterior-posterior resection guide is moved posteriorly until ananterior feeler gauge of the anterior-posterior resection guide contactsthe anterior cortex of the femur. Additional anterior-posterioradjustments can be made using an anterior-posterior positioning screwwhich moves the resection guide in the anterior-posterior direction insmall increments with respect to the feeler gauge. Proper positioning isconfirmed by examining the anterior-posterior resection guide to ensurethat about 2 mm to 4 mm of posterior condyle is visible under theresection guide.

A locking screw is tightened to secure the anterior-posterior resectionguide once it has been positioned as desired and slots defined in theguide are used to complete various other cuts, such as the anterior andposterior chamfer cuts. Additional guides are attached in a similarmanner to make other cuts. After all of the cuts have been made, thedistal femur has a shape congruent to the attachment surface of thefemoral component and the femoral component can be attached to thedistal femur.

During this process, a sometimes difficult aspect of femoral componentsizing is selecting a size for the femoral component when the femur,which has a natural biological variation in size and morphology frompatient to patient, falls in between two sizes. The ADVANCE® brandsingle reference point knee replacement system generally recommends thata smaller size be selected in such a situation to avoid “over-stuffing”the knee in flexion, in other words, to avoid a knee that is too tightand resists full extension. Of course, selecting a smaller size can alsoresult in a somewhat increased laxity of the joint at high knee flexionangles.

In addition to the ADVANCE® Single Reference Point brand kneereplacement system, other systems are used for preparing the femur forattachment of a femoral prosthesis. Another single reference pointsystem is described in U.S. Pat. No. 4,474,177 to Whiteside. Also,systems that do not use a single reference point can be employed. Forexample, there is also an ADVANCE® brand distal cut first kneereplacement system that uses an intramedullary rod as a reference pointto guide an initial distal cut. However, the remaining surgical steps,such as femoral component sizing and the anterior-posterior cuts, arereferenced off of the resected distal femoral surface.

Despite the effectiveness of the above-listed knee replacement systems,additional improvements in systems and methods for preparing the distalfemur for attachment of a femoral component are always desirable.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the invention to provide instruments and methods foruse in minimally invasive total knee arthroplasty.

It is another object of the invention to provide instruments thatimprove the ease and accuracy of minimally invasive total kneearthroplasty procedures.

It is another object of the invention to provide surgeons with variousoptions for performing minimally invasive total knee arthroplasty.

The foregoing and other objects and advantages of the invention areachieved using the various instruments and procedures described herein.Of the various instruments described herein, the claims of the presentapplication are directed to an anti-backout stylus instrument assembly.The anti-backout stylus instrument assembly comprises, generally, astylus configured for insertion into a locking stylus holder and alocking stylus holder. The locking stylus holder is configured to engagethe stylus at a series of discrete positions during insertion of thestylus into the locking stylus holder. The locking stylus holder is alsoconfigured to prevent the stylus from being withdrawn to a previous oneof the discrete positions, which prevents inadvertent backing out of thestylus from the locking stylus holder. The discrete positions arepreferably defined by detents formed on the stylus and a stop member onthe locking stylus holder. The locking stylus holder can be provided onan anterior rough cut guide, with the anterior rough cut guidepreferably mountable on an intramedullary rod in the femur.

The assembly is preferably provided with a disengagement member on thelocking stylus holder. The disengagement member is configured toselectively disengage the locking stylus holder from the stylus, andthereby allow the stylus to be withdrawn through the stylus holder. Thedisengagement member preferably comprises a part of the stylus bore ofthe locking stylus holder being formed by a biased button, with thebiased button configured such that a user can selectively backout thestylus from the locking stylus holder by depressing the biased buttonand simultaneously pulling the stylus rearward. The biased buttonpreferably has a stop member on a lower interior wall, the biased buttonnormally biased upward such that the stop member is positioned to engageone of a series of detents formed along a lower surface of an engagementportion of the stylus. The biased button is preferably biased by acaptured spring.

In a preferred embodiment, each of the discrete positions matches aparticular femoral size, such that each engagement of one of thediscrete positions by the locking stylus holder indicates a femoralsize. Each engagement of one of the discrete positions by the lockingstylus holder produces a sound, such that the sound provides anindication of a femoral size. Femoral size markings can also be providedon the stylus for use in visually determining a femoral size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred anterior-medial approach for use in thecarrying out the procedures of the invention.

FIG. 1P provides a perspective view of one preferred embodiment of anintramedullary rod for use in carrying out the procedures of theinvention.

FIG. 1B provides a perspective view of one preferred embodiment of anintramedullary rod having a detachable guide mount.

FIG. 2 shows a perspective view of one preferred embodiment of a medialdistal cut paddle and a medial distal cut guide mounted on anintramedullary rod, along with a resection of the medial distal femur.

FIG. 2P provides a perspective view of one preferred embodiment of amedial distal cut paddle.

FIG. 2B provides a perspective view of one preferred embodiment of amedial distal cut guide.

FIG. 2C provides a perspective view of one preferred embodiment of amedial distal cut guide.

FIG. 2D provides a perspective view of one preferred embodiment of amedial distal cut guide.

FIG. 3 shows a perspective view of one preferred embodiment of ananterior-posterior positioning caliper mounted on an intramedullary rodfor use in sizing a femur and translating a reference point from theintramedullary rod to a secondary reference point on the medial distalcut femur.

FIG. 3P provides a perspective view of one preferred embodiment of ananterior-posterior positioning caliper, and featuring a view of aremovable stylus.

FIG. 3B provides a perspective view of one preferred embodiment of ananterior-posterior positioning caliper.

FIG. 4 shows a perspective view of one preferred embodiment of aposterior sizing caliper mounted on the medial distal cut femur withreference to the secondary reference point.

FIG. 4P provides a perspective view of one preferred embodiment of aposterior sizing caliper.

FIGS. 4B-1, 4B-2, 4B-3, and 4B-4 provide a perspective view of onepreferred embodiment of a universal anterior-posterior positioning andposterior sizing caliper.

FIG. 5 shows a perspective view of one preferred embodiment of a cutblock mounted on the medial distal cut femur with reference to thesecondary reference point, and further showing anterior, posterior andchamfer cuts.

FIG. 5P provides a perspective view of one preferred embodiment of a cutblock.

FIG. 5C provides a perspective view of one preferred embodiment of cutblocks having an intramedullary rod aperture and a peg for use inmounting the blocks on the distal femur.

FIG. 5D provides a perspective view of one preferred embodiment of aproximal side of the cut blocks of FIG. 5C.

FIG. 6P shows a perspective view of one preferred embodiment of alateral distal cut guide mounted on the medial distal cut femur for usein resecting the lateral distal femur.

FIG. 6B shows a medial side view of the lateral distal cut guide of FIG.6A, and further shows a distal lateral cut slot formed between thelateral distal cut guide and the resected surface of the medial distalcut femur.

FIG. 6C shows a perspective view of the lateral distal cut guide of FIG.6A after completion of the resection of the lateral distal femur.

FIG. 6D provides a perspective view of one preferred embodiment of aleft and right pair of lateral distal cut guides.

FIG. 7 shows an alternative preferred embodiment of a lateral distal cutguide.

FIG. 8 provides a perspective view of one preferred embodiment of alateral distal cut guide.

FIG. 9 is a transverse view of the distal femur 301 showing a preferredorientation of the medial distal rough cut.

FIGS. 10, 11P, 11B, 12, 13P, 13B, 13C, and 14-18 provide views of stepsin a preferred MIS anterior rough cut procedure.

FIGS. 19P and 19B show preferred configurations of a sizer for use inMIS anterior rough cut procedures.

FIGS. 20P, 20B, 20C and 20D show preferred embodiments of a distal IMpaddle configured for use in an MIS anterior rough cut procedure.

FIGS. 21P, 21B, 21C, 21D, 21E, 21F, and 21G show embodiments of arotatable distal IM rod paddle which can be rotated about the IM rod andsecured into a correct orientation using a self-alignment feature.

FIGS. 22P and 22B show preferred embodiments of a modular quickconnector configured for use in an MIS anterior rough cut procedure.

FIG. 23 shows preferred embodiments of a distal cut resection guideconfigured for use MIS TKA procedures.

FIGS. 24P, 24C, and 24B show preferred embodiments of a recut guideconfigured for use in MIS TKA procedures.

FIGS. 25P, 25B, 25C, and 25D show preferred embodiments of an anteriorrough cut femoral resection block.

FIGS. 26P, 26B, 26C, and 26D show preferred embodiments of an anteriorrough cut femoral resection block having a medialized configuration.

FIGS. 27P, 27B, 27C, and 27D show preferred embodiments of a trialsulcus resection guide configured for use in MIS TKA procedures.

FIGS. 28P, 28B, 28C, and 28D show preferred embodiments of a sulcusresection guide configured for use in MIS TKA procedures.

FIGS. 29P and 29B show preferred embodiments of a two arm alignmentguide configured for use in an MIS TKA procedures.

FIG. 30 shows views of a cut guide for use in making an anterior roughcut.

FIG. 31 shows a front elevational view of a universal anterior-posteriorpositioning and posterior sizing caliper.

FIG. 32 shows a rear view of the universal anterior-posteriorpositioning and posterior sizing caliper shown FIG. 31.

FIG. 33 shows a cross-sectional view of the stylus holder of theuniversal anterior-posterior positioning and posterior sizing calipershown FIGS. 31 and 32.

FIG. 34 shows a cross-sectional view of a reference portion of theuniversal anterior-posterior positioning and posterior sizing calipershown FIGS. 31 and 32.

FIG. 35 shows a perspective view of a top loading sizing caliper.

FIG. 36 shows a front elevational view of the top loading sizing caliperof FIG. 35.

FIG. 37 shows a rear view of a top loading sizing caliper of FIGS. 35and 36.

FIG. 38 shows a side view of a top loading sizing caliper.

FIG. 39 shows a perspective view of a portion of the top loading sizingcaliper of FIGS. 35 and 36.

FIG. 40 shows a top view of a top loading sizing caliper.

FIG. 41 shows a perspective view of a paddle portion top loading sizingcaliper of FIGS. 35 and 36.

FIG. 42 shows a side view of the paddle portion top loading sizingcaliper of FIG. 41. FIG. 43 shows a top view of the paddle portion toploading sizing caliper of FIGS. 41 and 42.

FIG. 44 shows a perspective view of a sizer portion of the paddleportion top loading sizing caliper of FIGS. 35 and 36.

FIG. 45 shows a side view of a sizer portion of the paddle portion toploading sizing caliper of FIGS. 35 and 36.

FIG. 46 shows a top view of a sizer portion of the paddle portion toploading sizing caliper of FIGS. 35 and 36.

FIG. 47 shows an edge on view of a sizer portion of the paddle portiontop loading sizing caliper of FIGS. 35 and 36.

FIG. 48 shows a side view of a reference portion of the paddle portiontop loading sizing caliper of FIGS. 35 and 36.

FIG. 49 shows a perspective view of a reference portion of the paddleportion top loading sizing caliper of FIGS. 35 and 36.

FIG. 50 shows an end view of a reference portion of the paddle portiontop loading sizing caliper of FIGS. 35 and 36.

FIG. 51 shows a perspective view of a combined caliper portion of thepaddle portion top loading sizing caliper of FIGS. 35 and 36.

FIG. 52 shows a top side view of a combined caliper portion of thepaddle portion top loading sizing caliper of FIGS. 35 and 36.

FIG. 53 shows a bottom side view of a combined caliper portion of thepaddle portion top loading sizing caliper of FIGS. 35 and 36.

FIG. 54 shows a perspective view of a sizer portion of the paddleportion top loading sizing caliper of FIGS. 35 and 36.

FIG. 55 shows a side view of a sizer portion of the paddle portion toploading sizing caliper of FIGS. 35 and 36.

FIG. 56 shows a top view of a sizer portion of the paddle portion toploading sizing caliper of FIGS. 35 and 36.

FIG. 57 shows a side view of a sizer portion of the paddle portion toploading sizing caliper of FIGS. 35 and 36.

FIG. 58 shows a perspective view of a portion of the top loading sizingcaliper similar to FIGS. 39 and 40.

FIG. 59 shows a top view of a top loading sizing caliper similar toFIGS. 39 and 40.

FIG. 60 shows a perspective view of a reference portion of the paddleportion top loading sizing caliper.

FIG. 61 shows a top side view of a reference portion of the paddleportion top loading sizing caliper.

FIG. 62 shows an edge view of a reference portion of the paddle portiontop loading sizing caliper.

FIG. 63 shows an anterior stylus for use with of the paddle portion toploading sizing caliper.

FIG. 64 shows further aspects of the anterior stylus for use with of thepaddle portion top loading sizing caliper.

FIG. 65 shows a locking stylus holder for an anti-backout stylus.

FIG. 66 shows a top view of the locking stylus of FIG. 65.

FIG. 67 shows a side view of a stylus configured for use with ananti-backout stylus.

FIG. 68 shows an exploded view of a patella clamp and inseret portionthereof.

FIG. 69 shows a top view of an insert portion of the patella clamp shownin FIG. 68.

FIG. 70 shows a top view of the patella clamp shown in FIGS. 68 and 69.

PREFERRED EMBODIMENTS OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

As shown in the drawings and discussed in detail below, the inventiongenerally comprises instruments and surgical techniques for performing aminimally invasive resection of a distal femur using a medial approach.The instruments and techniques of the invention allow a total kneearthroplasty (“TKA”) to be performed through a single incision.

Quad Sparing Anterior Medial Approach

As indicated in FIG. 1, the preferred approach for the procedures of theinvention is generally anterior-medial through an incision commencing atapproximately the proximal or superior end of the patella and extendingdistally in a generally sagittal orientation. The preferred incision isapproximately twice the length of the patella (about 4 to 5 inches or 10to 13 cm).

Patella Resection

To assist in providing a minimally invasive approach, the patella isresected at the beginning of the procedure. The patella resection can becarried out using instruments and techniques known to those of skill inthe art.

Because the patella is prepared at the beginning of the procedure, thepatella can potentially be damaged during later stages of the operation.To avoid damage, the patella is optionally fitted with a removable capthat is configured to protect the resected surface and/or the peripheraledges of the patella, in manner known to those of skill in the art.

Alignment of Intramedullary Rod

As indicated in FIG. 1, a fixed reference for the resection procedure iscreated by inserting an intramedullary rod 10 into the intramedullarycanal of the femur. The intramedullary rod 10 is positioned in thebottom of the sulcus in a manner known to those of skill in the art (seee.g. U.S. Pat. No. 4,474,177, which is incorporated herein byreference). The alignment or final rotational position of theintramedullary rod 10 can be set using an alignment guide, such as amodified trochlear axis guide (see e.g. U.S. Pat. No. 6,159,217, whichis incorporated herein by reference) or a crosshair alignment guide. Aswill be discussed in further detail below, the final rotational positionof the intramedullary rod 10 provides a fixed reference point that isused to determine the final rotation of the implant, which assists inproviding a minimally invasive approach.

A preferred embodiment of an intramedullary rod 10 for use in theinvention is shown in FIG. 1A. The embodiment of FIG. 1A is a one pieceor unibody rod having an intramedullary stem 12 on a proximal end and aguide mount 14 portion on a distal end. The guide mount 14 has anon-circumferential cross-section in order to prevent rotation ofcutting guide instruments when mounted on the guide mount 14. In thepreferred embodiment shown in FIG. 1, the cross-section has a race trackor modified ellipsoidal configuration having a pair of substantiallyparallel flat surfaces interposed between oppositely oriented curvedsurfaces. An aperture 15 preferably extends through the guide mount 14.

As shown in FIG. 1A, a stop member 19 is positioned proximal to theguide mount 14 for preventing the guide mount portion 14 from enteringthe intramedullary canal. As shown in FIG. 1A, the stop member 19preferably comprises two or more tabs extending axially from theintramedullary rod. One or a plurality of anti-rotation fins 13 arefixed proximal to the stop 19 for preventing rotation of theintramedullary rod 10 following insertion into the intramedullary canal.

FIG. 1B shows an alternative embodiment of an intramedullary rod 10having a removable guide mount 14. The removable guide mount 14 can beselectively locked into a fixed orientation on the stem portion 12 ofthe intramedullary rod 10. In one embodiment, the removable guide mount14 threads onto the intramedullary rod 10. The removable guide mount 14can be removed to allow the knee to be flexed or extended for improvedvisualization without losing anchor position. In one embodiment, theintramedullary rod 10 is configured to provide a recessed intramedullaryrod 10 in which the entire body of the intramedullary rod 10 residesinside of the intramedullary canal, including the distal end of the rod10. The removable guide mount 14 can be provided with a threaded shafton a proximal end, the shaft sized to thread into a threaded bore on adistal end of the recessed intramedullary rod 10. A recessedintramedullary rod 10 and removable guide mount 14 combination allows afull distal cut, including a full distal cut first, to be made from ananterior or medial approach without impingement by the recessedintramedullary rod 10. In both the unibody and two part intramedullaryrod 10 embodiments, the guide mount 14 is preferably sized andconfigured to provide a smaller attachment area than that ofconventional intramedullary rods, which assists in providing a minimallyinvasive approach.

Medial Distal Cut

As indicated in FIG. 2, the resection procedure of the inventionpreferably uses a medial distal cut first. As shown in FIG. 2, a medialdistal cut paddle 30 and a medial distal cut guide 50 are attached tothe intramedullary rod 10 for use in making the medial distal cut first.

As shown in FIG. 2, the medial distal cut paddle 30 includes a platform31 which preferably has a flat profile on at least a proximal sidethereof. As shown in the preferred embodiment of FIG. 2A, the medialdistal cut paddle 30 has an intramedullary rod aperture 32 for use inattaching the medial distal cut paddle 30 to the intramedullary rod 10.As shown in FIG. 2A, the intramedullary rod aperture 32 is sized andconfigured to closely receive the guide mount 14 of the intramedullaryrod 10, to thereby prevent rotation of the medial distal cut paddle 30relative to the intramedullary rod 10. A clamp bolt 34 threads throughthe medial distal cut paddle 30 in association with the intramedullaryrod aperture 32 such that a distal end of the clamp bolt 34 selectivelyengages the guide mount 14 of the intramedullary rod 10, thus preventingthe medial distal cut paddle 30 from sliding along the guide mount 14.As indicated in FIG. 2, the medial distal cut paddle 30 is seated on theintramedullary rod 10 until the platform 31 contacts the most prominentportion of the medial distal condyle. As will be discussed in furtherdetail below, fixing the medial distal cut paddle 30 on the guide mount14 of the intramedullary rod 10 provides a fixed frame of reference thatis later translated to the medial distal femur.

FIG. 2B shows a preferred embodiment of a medial distal cut guide 50 foruse with the medial distal cut paddle 30. As shown in FIG. 2B, themedial distal cut guide 50 includes a generally flattened cut guideportion 52 having a cutting slot 53 formed therethrough for receiving aconventional saw blade (not shown). The medial distal cut guide 50includes a stem portion 54, which is connected to the cut guide portion52 via a curved or offset section 55. In a surgical kit, a plurality ofmedial distal cut guides 50 are preferably provided, with each guide 50having a different size offset 55 in order to allow a surgeon to selectan appropriate resection depth for the medial distal cut. As indicatedin FIG. 2, the curved section of the offset 55 offsets the cutting slot53 from the stem portion 54, and thus from the platform 31 of the medialdistal cut paddle 30. The medial distal cut guide 50 can optionally beprovided with one or more fixation bores 59 on a proximal side of thecut guide portion 52 for use in fixing the cut guide portion 52 on thefemur with pins or screws. The cut guide portion 52 preferably has acurved or arcuate shape in order to better fit the anatomy of the distalcondyle. In a surgical kit, the stem 54 can be provided in a variety oflengths to accommodate different sizes of femurs.

In FIG. 2, the medial distal condyle cut guide 50 is shown attached tothe medial distal cut paddle 30. As shown in FIG. 2A, the medial distalcut paddle 30 has a cut guide bore 36 formed through the platformportion 31. The cut guide bore 36 is sized and configured to closelyreceive the stem portion 54 of the medial distal cut guide 50 in asliding engagement. The sliding engagement between the stem 54 and cutguide bore 36 allows for selective positioning of the cut guide portion52 relative to the distal end of the femur. Additionally, the cut guidebore 36 is oriented at a selected angle relative to the guide mount 14and intramedullary rod aperture 32, such that the cut guide portion 52can be used through an anterior-medial incision. As shown in FIG. 2, aclamp bolt 38 threads through the distal condyle platform 31 inassociation with the cut guide bore 36 for use in selectively lockingthe stem 54 of the distal cut guide 50 relative to distal condyleplatform 30. Optionally, a second cut guide bore (not shown) can beadded to the distal condyle platform 30 to provide an option for a moremedial approach.

FIGS. 2C and 2D show an alternative preferred embodiment in which thestem 54 of the medial distal cut guide 50 is slidingly attached to thecut guide portion 52. This feature allows a surgeon additional optionsfor selectively positioning the cut guide portion 52 in order tooptimize the direction of the distal resection. The positionable distalcut guide 50 of FIGS. 2C and 2D has a locking means for use in lockingthe stem 54 is a selected position relative to the cut guide portion 52.In the preferred embodiment shown in FIGS. 2C and 2D, the locking meansincludes a pair of retaining tracks 60A, 60B. An eye 57 is formed on aproximal end of the stem 54. A bolt 68 passes through the stem eye 57 inan inverted position, such that the head 69 of the bolt 68 is retainedby the opposing tracks 60A, 60B of the cut guide portion 52. A nut 67 isthreaded onto the bolt 68. When the nut 67 is rotated to decrease thedistance between the nut 67 and the bolt head 69, the nut 67 compressesthe eye 57 of the stem 54 against the retaining tracks 60A, 60B, whichretains the stem 54 in a fixed position on the cut guide portion 53. Thenut 67 can be loosened in order to selectively reposition the stem 54.The adjustable distal cut guide 50 of FIGS. 2C and 2D allows the surgeonto select an approach that is more medial, anterior-medial or anterior,depending on the preference of the surgeon and the needs of theparticular case, which further contributes to a minimally invasiveapproach.

FIG. 9 is a transverse view of the distal femur 301 showing a preferredorientation of the medial distal rough cut using the instruments andtechniques described herein. The approximate anterior-medial slope ofthe medial distal condyle 302M is indicated by line 360. Line 50indicates the preferred orientation of the medial distal cut guide 50relative to the anterior-medial slope 360 of the medial distal condyle302M. A preferred orientation of the medial distal rough cut isindicated by arrow 360C. As indicated in FIG. 9, the medial distal roughcut 360C is preferably made substantially along the anterior-medialslope 360 of the medial distal condyle 302M. The cut 360C is directedanterior-medially at an angle that is roughly perpendicular to the slopeof anterior-medial slope 360 of the medial distal condyle 302M.

Position of Anterior Reference

After the medial distal condyle has been resected, the femur is sized.Sizing is preferably done in a two step procedure that contributes tothe minimally invasive approach of the invention. In the first step,shown in FIG. 3, an anterior-posterior positioning caliper or anteriorreference jig 80 is used to establish an anterior reference 303 (e.g. apeg position or an arbitrary reference point). In the second step, shownin FIG. 4, a posterior sizing caliper or posterior sizer 120 is used todetermine the size of the femoral implant with reference to the anteriorreference and the medial posterior condyle (see FIG. 4).

FIGS. 3 and 3A show alternative preferred embodiments of an A-Ppositioning caliper or anterior reference jig 80 for use in establishingan anterior reference on the resected medial distal condyle. The A-Ppositioning caliper 80 is configured to allow for ready translation ofrotation or position from the intramedullary rod 10 to the medialcondyle. FIG. 3 shows the A-P positioning caliper 80 positioned on theguide mount 14 of the intramedullary rod 10. As shown in FIG. 3, aproximal end of an anterior stylus 100 contacts the anterior cortex ofthe femur. As indicated in FIG. 3, a drill guide 82 is used to establisha reference point on the resected medial distal femur. Details ofpreferred embodiments of the A-P positioning caliper 80 will now bedescribed, with particular reference to FIG. 3A.

The A-P positioning caliper 80 shown in FIG. 3A includes a reference bar81 that has an inverted “L” configuration. As shown in FIG. 3A, thereference bar 81 includes a vertical bar portion 85 and a horizontal barportion 86 extending from an upper end of the vertical bar portion 85. Avertical retaining track 87 is formed along a medial side of thevertical bar portion 85 of the reference bar 81. A retaining arm 90 isslidably engaged to the vertical track 87 in a substantiallyperpendicular relationship to the vertical bar portion 85. A stop 88preferably retains the retaining arm 90 on the reference bar 81 when theretaining arm 90 reaches the bottom of the vertical track 87. Theretaining arm 90 of the A-P positioning caliper 80 includes anintramedullary rod aperture 92, which is sized to closely receive theintramedullary rod 10. A locking means such as a clamp bolt 94 isassociated with the intramedullary rod aperture 92 for use inselectively locking the retaining arm 90 on the guide mount 14 of theintramedullary rod 10. As indicated in FIG. 3, the retaining arm 90remains in a fixed position on the intramedullary rod 10, while thereference bar 81 can be selectively raised or lowered along theretaining arm 90 for use in anterior-posterior positioning.

As shown in FIG. 3A, a set of calibration marks or a calibration scale89 is provided on the vertical bar portion 85 of the reference bar 81for use in modifying the A-P position or to provide a reference for thenext block. One or more reference marks 99 are also provided on theretaining arm 90 for use in conjunction with the calibration scale 89.

As shown in FIG. 3A, an anterior stylus 100 is attached to an upperportion of the A-P positioning caliper 80. The stylus 100 is preferablyremovable from the A-P positioning caliper 80. In the embodiment shownin FIG. 3A, the A-P positioning caliper 80 includes a stylus holder 101which projects upward from the horizontal bar portion 86. The stylusholder 101 includes a stylus bore 102 for receiving an anterior stylus100. The stylus bore 102 is sized and configured to closely receive aportion of the stylus 100. In the embodiment of FIG. 3A, the stylus 100can slide proximally and distally to ease insertion, which assists inproviding a minimally invasive approach. The anterior stylus 100 isavailable in various configurations (e.g. standard; +2 mm; −2 mm) foruse in making secondary adjustments. Although the stylus 100 isdetachable, a locking means may be provided for selectively locking thestylus 100 in position on the A-P positioning caliper 80. The embodimentof FIG. 3B includes a two part horizontal bar portion 86A, 86B having astationary portion 86A and a positionable portion 86B. The positionableportion 86B slidably engages the stationary portion 86A. This embodimentallows the stylus 100 to slide proximally and distally to easeinsertion, and thus assists in providing a minimally invasive approach.

As shown in FIG. 3A, a drill guide 82 extends from the vertical barportion 85 of the A-P positioning caliper 80. The drill guide isprovided with one or more drill holes 83 for use in establishing an A-Pposition or secondary reference point 303 on the medial cut of thedistal femur 301, and thus to translate rotation or position from theintramedullary rod 10 to the medial condyle. Because the A-P positioningcaliper 80 attaches to the intramedullary rod 10, only one referencehole 83 is required for translating the position of the secondaryreference point. Alternatively, a plurality of holes 83 can be used toestablish the secondary reference point or points 303, which serves totranslate both position and rotation from the primary reference point.The secondary reference point 303 can have a non-symmetric geometry. Ina preferred embodiment, the drill guide 82 is provided with two drillholes 83, as shown in FIG. 3. The secondary reference position 303 mayor may not be the position of the final implant. Additionally, the A-Ppositioning caliper 80 can be used with or without an intramedullary rod10, for example by inserting the peg(s) 123 of the posterior sizingcaliper 120 into the hole(s) 83 of the A-P positioning caliper 80.

The A-P positioning caliper 80 preferably has a universal configuration,which allows it to be used for a left or a right knee procedure. Auniversal configuration reduces the number of instruments that must beprovided in an MIS surgical kit.

Posterior Sizing

As indicated in FIG. 4, once the secondary reference point 303 has beenestablished on the cut medial distal condyle, sizing is determined usinga separate posterior sizing caliper or posterior sizer 120. In order tominimize anterior exposure in a minimally invasive procedure, femoralsizing is preferably carried out using the anterior medial femoralcondyle or the anterior medial condyle ridge, rather than the anteriorlateral cortex. Sizing can also be carried out using the anteriorlateral condyle.

As shown in FIG. 4A, the posterior sizer 120 generally comprises a sizerportion 130 in a sliding relationship with a reference portion 121. Asshown in FIG. 4A, a distal surface of the reference portion 121 isprovided with pegs or projections 123. The pegs 123 are sized andpositioned to match the drill hole or holes 83 of the A-P positioningcaliper 80, such that the reference portion 121 is affixed to the cutmedial distal femur with reference to the secondary reference point 303(see FIG. 4). As shown in FIG. 4A, the reference portion 121 is providedwith opposing tracks 127A, 127B for slidably engaging a sizer portion130 of the posterior sizer 120. As shown in FIG. 4A, the sizer portion130 has a vertical bar portion 135 and at least one posterior paddleportion 136, the bar portion 135 and paddle portion 136 together forminga generally L-shaped configuration. A locking means is preferablyprovided for use in selectively locking the sizer portion 130 in aselected position on the reference portion 121. In the preferredembodiment shown in FIG. 4A, the locking means is a clamp bolt 124 thatis threadably engaged to the reference portion 121. The vertical barportion 135 is provided with a lengthwise slot 134 to accommodatesliding of the locking means 124.

Calibration marks 139 and reference marks 129 are provided for use indetermining the size of the femoral implant. As shown in FIG. 4A, thecalibration marks 139 are on the sizer portion 130 while the referencemarks 129 are on the reference portion 121.

As shown in FIG. 4, the peg or pegs 123 of the posterior sizer 120 areinserted into the secondary reference point or points 303 on the medialdistal femur. Sizing is achieved by touching the posterior paddle 136 ofthe posterior sizer 120 to the most prominent portion of the posteriorcondyle. In a single peg 123 embodiment, the posterior sizer 120 can berotated about the anterior referencing point to provide optimal sizing.

Alternatively, the peg(s) 123 of the posterior sizer 120 can be insertedinto the drill holes 83 of the A-P positioning caliper 80 prior toremoval of the caliper 80 from the IM rod 10. The latter technique isparticularly suited to making adjustments depending on sizing (e.g. halfsizes).

Alternatively, sizing can be accomplished using a combinedanterior-posterior positioning and posterior sizing caliper, such as theuniversal embodiment 140 shown in FIG. 4B. The combined caliper 140includes many of the features described above, such as a removablestylus 100 slidably engaged to a stylus holder 101, a reference portion121 and a sizer portion 130. The combined caliper 140 is preferablyprovided with a pair of spaced apart posterior paddles 136.

Box Geometry Preparation

Once the proper size of the femoral implant has been determined, anappropriately sized cut block 150 is selected and placed over a singlecondyle. In the medial approach shown in FIG. 5, the cutblock 150 isplaced over the medial condyle. As indicated in FIG. 5, although the cutblock 150 is mounted only on the medial condyle, the cut block 150 isused to make an anterior cut 354A, a posterior cut 354P, an anteriorchamfer cut 355A, and a posterior chamfer cut 355P on both the medialand lateral aspects of the distal femur. After this step, all of the boxcuts have been completed with the exception of the distal lateralcondyle.

FIGS. 5C and 5D show left and right versions of preferred embodiments ofa cut block 150 that can be attached to the intramedullary rod 10 and tothe secondary reference point 303. FIG. 5C shows the distal side of thecut block 150, while FIG. 5D shows the proximal side of the cut block150. The block portion 151 of the cut block is provided with four slots:an anterior cut slot 154A; a posterior cut slot 154P, an anteriorchamfer slot 155A; and a posterior chamfer slot 155P. As viewed from thedistal side shown in FIG. 5D, a single entry slot 155 provides commonaccess to both the anterior chamfer slot 155A and the posterior chamferslot 155P. Each of the slots is open along the patellar groove side ofthe cut block 150 to allow for resection of the lateral condyle.

As shown in FIG. 5D, a proximal side of the cut block 150 is providedwith at least one peg or projection 153 for use in attaching the cutblock 150 to the secondary reference point 303 of the distal femur.Fixation apertures 157 are provided for use in temporarily screwing thecut block 150 to the femur in a manner known to those of skill in theart, which stabilizes the cut block 150 during resection. The cut block150 shown in FIGS. 5C and 5D has an intramedullary rod retaining member160. The intermedullary rod retaining member 160 includes an IM rodaperture 162 that is sized and configured to closely receive the cutguide mount 14 of the intramedullary rod 10. In the embodiment shown inFIG. 5C, the intramedullary rod retaining member 160 is slidably engagedto the patellar groove side of the cut block 150 for use in selecting ananterior-posterior position. Alternatively, the intramedullary rodretaining member 160 may be fixed to the cut block 150.

As shown in FIG. 5C, a calibration scale is provided on the distal sideof the cut block 150. The calibration scale 159 matches the scale of theA-P positioning caliper 80. As indicated in FIGS. 5C and 5D, the cutblock 150 is provided in left and right configurations.

The block portion 151 of the two peg cut clock 150 has a configurationand features that are similar or identical to those of the cut blockportion 151 of the intramedullary rod cut block shown in FIGS. 5C and5D. However, the cut block 150 lacks an intramedullary rod retainingportion 160, and instead is provided with two or more pegs 153 on theproximal side. In the preferred embodiment, the cut block 150 has twopegs 153. Use of a multi-pegged cut block 150 allows box cuts to be madeafter the intramedullary nail 10 has been removed. The pegs 153 arepreferably sized and configured to match the secondary reference points303 that were created with the drill guide 82 of the A-P positioningcaliper 80. Since the intramedullary rod 10 is not available as areference point, the pegs 153 and holes 303 provide the reference point.Together, the pegs 153 prevent rotational displacement of the cut block150 relative to the reference points, which allows the surgeon toprepare the box geometry in the correct rotation and orientation. Inaddition to circular pegs, non-circular geometries can be used tomaintain orientation of the cut block 150, including, for example, aslot and fin or an oval hole and oval peg.

In addition to the features described above, the geometry of the cutblock 150 is configured to provide for minimized instrument size and foroptimizing positioning when using MIS techniques. The cut blocks 150shown in the drawings include rounded edges along the outer edge, aswell as chamfers along the distal side.

Lateral Condyle Resection

After completion of the medial and lateral resections, the cut block 150is removed. At this point, all of the box geometry cuts have been madewith the exception of the distal lateral condyle resection. As shown inFIGS. 6 and 7, a lateral distal cut guide 170 is used to make thelateral distal condyle resection. As shown in FIGS. 6A and 6B, thelateral distal cut guide 170 is placed on the medial distal condyle351M. As will be explained in further detail below, the lateral condylecut guide 170 is configured to allow use of the resected bone of themedial distal condyle as the proximal wall or bottom of the distallateral cut slot 174. This feature minimizes the size of the lateralcondyle cut guide 170, which assists in providing a minimally invasiveapproach.

FIG. 6 shows one preferred embodiment of a lateral distal cut guide 170.In FIGS. 6A-6B, the lateral distal cut guide 170 is shown mounted on themedial distal cut femur 351M prior to resection of the lateral condyle351L. FIG. 6B provides a medial view of the and the lateral distal cutguide 170 mounted on the femur 300. As can be seen in FIG. 6B, thelateral distal cut guide 170 is configured such that a distal lateralcut slot 174 is formed between a distal wall portion 174D of the lateraldistal cut guide 170 and the flat surface of the medial distal cut femur351M (in the drawings, item number “174” is underlined to indicate thatthe distal lateral cut slot 170 is a space rather than a physicalobject). Additionally, the lateral distal cut guide 170 is configured toprovide an anterior wall portion 174A which forms the anterior limit ofthe distal lateral cut slot 174, and a posterior wall portion 174P,which forms the posterior limit of the distal lateral cut slot 174. Asshown in FIG. 6B, distal portions of the cut guide 170 are configured toclosely receive the cut portions of the medial distal cut femur 351M, tothereby assist in securely mounting the cut guide 170 on the distalfemur. Additionally, the cut guide 170 is sized and configured toprovide a desired width or tolerance to the distal lateral cut slot 174when the cut guide 170 is mounted on the femur, the desired width beingselected to maximize guidance and use of a surgical saw during thedistal lateral resection.

As can be appreciated from the medial view of FIG. 6B, by inserting asaw into the distal lateral cut slot 174 from the medial approach, thesurgeon can readily access and resect the lateral distal condyle 351Lwithout inadvertently damaging surrounding tissues. In FIG. 6C, thelateral distal femur has been resected to provide a cut lateral distalfemur 351L that is planar or substantially planar with the cut medialdistal femur 351M.

Fixation apertures 177 are provided on the lateral distal cut guide 170for use in selectively securing the cut guide 170 to the femur withscrews. The location of the fixation apertures 177 will vary dependingon the size and configuration of the lateral distal cut guide 170, butthe locations will preferably be selected to maximize the use ofavailable bone, maximize the structural strength of the lateral distalcut guide 170, and minimize trauma to the patient's bone. As shown inFIG. 6D, the lateral condyle cut guide 170 is available in left andright embodiments. The lateral condyle cut guide 170 is size specific.As shown in FIGS. 6C and 6D, the lateral distal cut guide 170 canoptionally be provided with anterior and posterior chamfer cut slots orguides 155A, 155P, which can be used in lieu of the chamfer cut slots155A, 155P on the cut block 150. Thus, in the embodiment of FIG. 6C, thelateral distal cut guide 170 can be used to make the chamfer cuts 354A,354P as well as the lateral distal cut 351L. The chamfer cut slots 155A,155P open toward the patellar groove in order to provide access to thelateral limits of the femur.

FIGS. 7-8 show an alternative lateral distal cut guide 170 whichpresents a smaller profile than that of FIG. 6, thus furthercontributing to a minimally invasive approach. The embodiment of FIG. 7forms a distal lateral cut slot 174 between a distal wall 174D and themedial distal cut femur 351M. However, the size of the anterior andposterior walls 174A, 174P of the distal lateral cut slot 174 isminimized in comparison to the embodiment of FIG. 6. In a preferredembodiment, the anterior and posterior walls 174A, 174P aresubstantially equal to the selected width of the distal lateral cut slot174, and are configured to rest on the plateau of the medial distal cutfemur 351M. As can be seen in FIG. 8, the fixation apertures 177preferably pass through or adjacent to the anterior and posterior walls174A, 174P in order to maximize use of available bone for fixation ofthe instrument.

A handle mount member 178 is fixed or formed on the distal surface ofthe lateral distal cut guide 170. The handle mount member 178 isprovided with a handle engagement means 179 for selectively mounting thelateral distal cut guide 170 on a conventional instrument handle. Thehandle engagement means 179 can be selected from those available in theprior art, such as threaded, dovetail or quick-connect. As indicated inFIGS. 7A, the handle mount 178 is oriented to optimize the angle ofentry through the incision, which further contributes to the minimallyinvasive approach.

When using the embodiment of FIG. 7, it may be preferable to completethe lateral distal cut prior to making the box cuts, since more bonewill be available for mounting the lateral distal cut guide 170. If usedafter the box cuts, the anterior-posterior dimension of the lateraldistal cut guide 170 of FIG. 7A may be sized substantially to the A-Pdimension of the medial distal cut femur 351M, in order to minimize thesize of the instrument while providing for maximal use of availablebone.

FIG. 30 shows views of a cut guide for use in making an anterior roughcut. The cut guide has a T configuration with a slot formed through thetop of the T. The cut guide is mounted on an A-P positioning calipersuch as the caliper shown in FIG. 3A.

FIG. 19 shows views of a sizing caliper that is used to size the distalfemur after making an anterior rough cut and a distal cut. The lowerpaddles are configured to rest against the femoral condyles. The upperextension rests on the anterior rough cut.

Variations in the order of the foregoing steps can be made withoutdeparting from the spirit and scope of the invention. For example, atthe surgeon's discretion, the distal lateral cut may be made prior tothe box geometry cuts. Further, some surgeons may find it advantageousto prepare the tibial plateau prior to carrying out the foregoingprocedures, in order to provide additional space within the knee cavityfor the minimally invasive femoral procedure.

The resections can be limited to just the distal cut or to a combinationof distal, anterior, posterior and chamfer cuts. Depending on the cutsperformed, this invention will allow the surgeon to size, prepare bonesurfaces, etc. in the preferred external femoral rotation. The conceptsdisclosed herein can be used with different MIS TKA surgical techniques,such as distal cut first, anterior rough cut, etc. The concepts can alsobe applied to non-MIS TKA instrumentation, as well as other orthopedicapplications, including tibial instrumentation. Although this procedurehas been described with reference to a medial approach, the foregoingtechniques and instruments can be adapted to a lateral approach. In alateral approach, the initial cut is made on the lateral distal femur,and the lateral distal cut femur 351L is then used to align and make theanterior, posterior, anterior chamfer, posterior chamfer and medialdistal cuts, in the manner described above for the medial approach.

Anterior Rough Cut Procedure

FIGS. 10-18 provides views of the steps used in an anterior rough cut(“ARC”) procedure using the ARC instruments disclosed herein. As shownin FIG. 10, the IM rod 10 is installed and properly oriented in thefemur 300. Alignment can be achieved using the two handle alignmentguide shown in FIG. 29, which is particularly suited for use in MIS kneeprocedures. As shown in FIG. 10, a distal IM paddle/IM alignment body500, such as the paddles 500 shown in FIGS. 33, 34 and 35, is slid downthe shaft of the valgus portion of the IM rod 10 until it contacts thedistal femur. The distal IM paddle 500 is then locked to the flats ofthe valgus rod 10 by tightening the locking set screw 512. Foradditional stability, pins may be placed in the pin holes 508 on thedistal face of the distal IM paddle 500.

As shown in FIGS. 11A-11B, an anterior rough cut guide 600, such as thetype shown in FIG. 65, is slid into the distal IM paddle 500. Thesupport bars 602 of the anterior rough cut guide 600 are slid into thesupport bar openings 520 of the distal IM paddle 500. As shown in FIG.12, the tip 100 of an anterior stylus 100 is slid through the stylusbore 102 of the ARC guide 600 for use in sizing the femur.

In a preferred embodiment, the ARC guide 600 is provided with a lockingstylus holder 101′ for use with an anti-backout stylus 100′. Theanti-backout stylus 100′ provides several functions that are useful inMIS procedures. The anti-backout stylus 100′ is easy to insert into thestylus bore 102 in MIS incisions, prevents inadvertent backing out ofthe stylus (which could result in an inaccurate anterior resection), andprovides both audio and visual sizing information. As shown in FIG. 65,part of the stylus bore 102 of the locking stylus holder 101′ is formedby a biased button 610. The biased button 610 includes a bore 612 forreceiving the anti-back out stylus 100′. The bore 612 of the biasedbutton 610 has a stop member 611 on a posterior wall. The biased button610 is normally biased anteriorly or upwards, such as by a capturedspring biasing means 614, such that the stop member 611 normally engagesdetents 105 formed along a posterior surface of an engagement portion ofthe anti-backout stylus 100′. As shown in FIGS. 66-67, each of thedetents 105 of the anti-backout stylus 101′ has an inclined proximalside 106 configured to slide over the stop member 611 when pushedforward, as well as a flat or declined distal side 107 configured toabut against the stop member 611 of the biased button 610. The detents105 allow the surgeon to slide the stylus 100′ forward (proximally), butprevent the surgeon from inadvertently backing out the stylus 100′(distally). However, the surgeon can selectively back out theanti-backout stylus 100′ simply by depressing the stylus button 610while simultaneously pulling the stylus 100′ distally. Depressing thebiased button 610 disengages the stop member 611 from the detents 105,permitting withdrawal of the stylus 100′. In FIG. 65, the locking stylusholder 101′ is shown mounted on an anterior rough cut guide 600, but theanti-backout concepts disclosed herein can be used with other types ofstyluses or sizing calipers. Additionally, while the anti-backout stylushas been described for use with TKA instruments, an anti-backout styluscould be adapted for use with other orthopedic instruments.

Each of the detents 105 on the anti-backout stylus 101′ is preferablypositioned to match a particular femoral size, which allows the stylus101′ to provide both visual and audio sizing information. For visualreference, femoral size markings are preferably provided on the anteriorportion of the stylus 100, preferably where the stylus meets the stylusholder 101. Additionally, as the stop member 611 snaps into positionagainst a detent 105, the instrument makes a clicking sound. As thesurgeon pushes the anti-backout stylus 100′ into the stylus bore 102,each click represents one femoral size. The stylus 100 is pushed untilthe number of clicks equals the estimated femoral size. The clicksprovide the surgeon with a non-visual means of verifying the size of thefemoral implant, which is useful in MIS procedures.

Other features of the anti-backout stylus 101′ that assist in MISprocedures include reduced profiles. When viewed from the side, theanti-backout stylus 101′ has a substantially flat portion 108 forsliding through the locking stylus holder 101′, a tip 110 on a forwardend, and a downwardly sloped portion 109 between the flat portion 108and the tip 110. To promote ease of insertion when inserting the stylus101′ into an incision, an upwardly sloped cutout 112 is preferablyformed along a posterior or lower side of the flat portion 108 in thearea adjacent the sloped portion 109 of the stylus 100′. A cutout 112 atthis location allows the stylus 100′ to slide over anatomical structuresencountered in MIS TKA procedures. Additionally, when viewed from thetop or bottom, the downwardly sloped portion 109 has a forward taper,i.e. the downwardly sloped portion 109 narrows toward the tip 110. Thistaper also allows the stylus 100′ to slide over or around anatomicalstructures encountered in MIS TKA procedures.

Once the depth of the anterior resection has been determined using theanterior stylus 100, the anterior rough cut resection slot 605 is fixedinto position by tightening the two set screws 525 on the distal face ofthe distal IM paddle 500. The ARC guide 600 is then removed from thedistal IM paddle 500.

As shown in FIGS. 13A and 13B, once the anterior rough cut has beenmade, a modular quick connector 640, preferably of the type shown inFIG. 22, with an attached distal crosshead 660 is inserted into thedistal IM paddle 500. Support bars 642 of the modular quick connector640 are configured to match the support bar openings 520 of the distalIM paddle 500. The modular connector 640 is configured to receive adistal resection guide 660, such as the distal cut guide shown in FIG.23, and to hold the guide 660 in a fixed position relative to the distalpaddle 500. The modular connector 640 includes a sliding locking button644. The sliding locking button 644 includes a stop portion 645configured to selectively engage an annular recess in the mounting stemof the crosshead. In the embodiment shown in FIG. 22, the locking button644 engages the mounting stem when the button is pushed upward, anddisengages when the button is pushed downward. The modular quickconnector 640 can be used in ARC or DCF procedures.

As indicated in FIG. 13B, the crosshead 660 is lowered as close aspossible to the anterior rough cut. In some cases, the crosshead 660will not touch the anterior rough cut. In a preferred embodiment, withthe crosshead 660 in the standard or primary position, 9 mm of thedistal femur will be resected from the prominent distal condyle. If adeeper resection (e.g. 11 mm; 13 mm) is needed, the crosshead 660 may berepositioned for a deeper secondary resection position by pushing thelocking button 644 of the modular quick connector 640 down and slidingthe crosshead proximally. The location of the secondary position ispreferably indicated with a marker (e.g. a “+4 mm” mark becomesvisible). The mounting stem of the crosshead 660 includes a secondannular recess positioned to engage the stop portion 645 with thecrosshead resection slot set at the secondary/deeper resection position.The crosshead 660 is then locked into the secondary resection positionby pushing the locking button 644 up.

After the resection amount is set, the crosshead 660 is pinned to theanterior cortex of the femur, preferably with two headless pins. Beforemaking the distal resection, the distal IM paddle 500, the modular quickconnector 640, and the IM rod 10 are removed from the femur. Pushingdown on the locking button 644 unlocks the crosshead 660 from themodular quick connector 640, which allows the remaining components to beremoved without dislodging the crosshead 660. With the distal IM paddle500 and modular quick connector still affixed to the valgus portion ofthe IM rod 10, a slap hammer and hook can be used to remove the IM rod10 and attached components from the femur. This leaves the crosshead 660on the anterior rough cut femur in the configuration shown in FIG. 13C.In a preferred embodiment, the crosshead 660 can be readjustedproximally by lifting the crosshead 660 from the headless pins and thensliding the headless pins through a second set of holes, which arepreferably marked to indicate the amount of reset, e.g. “+2 mm.” Adivergent pin hole is preferably provided in the crosshead 660, and ispreferably used to achieve additional stability. A distal resection isthen made using the resection slot 665 in the crosshead 660. Once thedistal resection has been made, the crosshead 660 is removed from thefemur. As shown in FIGS. 14-15, if additional resection is needed,anterior or distal recuts can be made, preferably using the recut guide680 shown in FIG. 24.

After the anterior rough cut and the distal cut have been made, thesurgeon sizes the femur. The A-P sizer 690 shown in FIG. 16 isparticularly adapted for sizing an anterior rough cut and distal cutfemur in MIS procedures. The small size and rounded edges of the A-Psizer 690 allow it to be maneuvered into position in the confines of anMIS procedure. As indicated in FIG. 16, the A-P femoral sizer 690 isplaced flush against the resected distal femur. The A-P sizer 690 isadjusted so that the feet or paddles 136 contact the posterior condylesand the anterior stylus 100 rests on the anterior rough cut. The femoralsize is indicated on the distal face of the A-P sizer 690. Resecting theproximal tibia before femoral sizing may facilitate placement of theposterior paddles 136 of the sizer under the posterior femoral condyles.

As shown in FIG. 17, after sizing, an appropriately sized ARC femoralresection block 700, preferably of the type shown in FIG. 25 or FIG. 26,is placed flush against the distal and anterior femoral surfaces. Thefemoral resection block 700 shown in FIG. 17 and FIG. 25 has severalfeatures that make the resection block 700 particularly suited foranterior rough cut MIS procedures. The femoral resection block 700 isuniversal, i.e. it can be used on either a left or right femur, whichreduces instrument inventory. An anterior flange 702 of the femoralresection block 700 is sized and configured to rest against the anteriorrough cut when the proximal face of the resection block 700 is flushagainst the distal rough cut. These features stabilize the femoralresection block 700 when operating in the confined spaces of MISprocedures. Additionally, the femoral resection block features pinoutriggers 705 fixed to opposing medial and lateral edges of the block700 for use in pinning the block 700 to the femur. The through bores ofthe pin outriggers 705 are preferably offset so as to provide enhancedfixation. The distance between the pin outriggers 705 is substantiallythe same as the M/L width of the corresponding femoral implant, whichallows the resection block to be narrower and thus easier to use in MISprocedures. The narrower size and the pin outriggers 705 allow thesurgeon to visualize the bone along the M/L edges of the resection block700, to verify proper M/L sizing using the pin outriggers 705, and topin the block 700 to the distal cut femur via the pin outriggers 705.The resection block 700 includes posterior 154P, posterior chamfer 155P,anterior 154A, and anterior chamfer 155A resection slots. Therecommended order of resections in the ARC procedure is posterior,posterior chamfer, anterior, and anterior chamfers. Use of unthreadedpins in the pin outriggers 705 is recommended in order to avoidpotential pin cross-threading and shearing. A narrow saw blade (12.5 mm)is recommended for the chamfer resections. For added stability, theresection block 700 can also be provided with secondary fixation holes710 through the face of the block 700. The pins must be removed from thesecondary fixation holes 710 prior to the chamfer resections.

The sulcus resection is preferably carried out using a sulcus resectionguide 720, such as the sulcus resection guide 720 shown in FIG. 18 andFIG. 28. The surgeon selects a sulcus resection guide 720 thatcorresponds in size to the femoral resection block 700 that was used tomake the resections. The sulcus resection guide 720 shown in FIG. 28includes cut-out areas 722 along the medial and lateral sides of thesulcus cut guide 720. The outer medial and lateral edges of the sulcusresection guide 720 substantially match the M/L dimension of the femoralimplant. The cut out areas 722 allow the surgeon to see the medial andlateral portions of the femur, which allows the surgeon to bettervisualize placement of the guide 720 as well as the quality of the bone.The top of the sulcus resection guide 720 rests on the resected anteriorfemoral cortex. The sulcus resection guide 720 is preferably lateralizedon the femur to reacquire the Q-angle. The sulcus resection guide 720 ispinned to the femur using the anterior and distal pairs of holes. Thetrochlear groove is resected using a saw blade on either the anterior orposterior angled surface and along the sides 726 of the central opening725 of the sulcus resection guide 720.

FIG. 27 shows a femoral trial sulcus resection guide 720 that can beused both as a femoral trial and to make a sulcus cut. The trial sulcusresection guide 720 features a removable patella groove portion 727,which slides into the opening 725 in the body of the trial. Theremovable patella groove 727 can be used to check patella fit, and canalso be removed from the trial body 720 in order to provide access forthe sulcus cut. A removable cut guide 730 can be mounted into holes onthe face of the implant for use in supporting a saw blade when making asulcus cut. The cut guide 730 can be provided with a resection slot (notshown) or a support bar 731. Once the sulcus cuts are complete, thesurgeon trials and implants in the conventional manner.

Aspects of preferred embodiments of instruments used in the anteriorrough cut procedure will now be described in further detail.

FIG. 20 shows an alternative embodiment of a distal IM rod paddle 500for mounting on an IM rod 10 for use in making anterior and distal cuts.FIG. 10 shows the distal paddle 500 on an IM rod. Each of the supportbar openings 520 are preferably provided with a grooved portion 522,which is sized and configured to closely receive a matching ridge 622 ofthe support bars 620 of modular inserts, such as of the anterior roughcut guide 600, the insert portion 580, or the modular quick connector640.

FIG. 21 shows an embodiment of a rotatable distal IM rod paddle 500which can be rotated about the IM rod 10 and secured into a correctorientation using a self-alignment feature. The rotatable IM rod paddle500 is particularly suited to MIS procedures because it allows thesurgeon to insert the paddle 500 onto the IM rod 10 in any degree ofrotation, rotate the paddle 500 on the IM rod 10 until a correctorientation is achieved, and then secure the paddle 500 on the rod 10 inthe correct orientation. Prior art paddles 500 were non-rotatable, andtherefore had to be placed on the IM rod 10 in the correct orientation,which can be difficult when operating under the confines encountered inMIS procedures. Prior art non-rotatable paddles tend to abut againsttissues within the incision, which makes it difficult to achieve theorientation needed for slipping the paddle onto the rod. With arotatable paddle 500, the surgeon can simply rotate the paddle withinthe incision until the IM rod aperture 510 passes over the end of thevalgus portion of the IM rod 10, without regard to the orientation ofthe paddle 500. This allows the surgeon to maneuver the rotatable paddle500 onto the rod 10 while avoiding contact between tissues andprotruding parts of the paddle 500, such as the paddle legs 506.

Rotation is achieved by providing the paddle 500 with an IM rod aperture510 that is configured to allow the paddle 500 to rotate on the IM rod10. The IM rod aperture 510 preferably has a round or cylindricalconfiguration, which permits 360 degree rotation on the rod 10. Thecircumference of the IM rod aperture 510 is preferably selected toclosely fit the opposing rounded sections of the applicable IM rod 10,such that lengthwise contact between the rounded sections of the IM rod10 and the round aperture 510 of the rotatable paddle 500 serves tosubstantially prevent rotation of the paddle 500 on the rod 10, exceptabout the axis of the valgus portion of the IM rod 10.

Additionally, the rotatable IM paddle 500 is provided with a means 550for selectively securing the paddle 500 in the correct orientation, i.e.for selectively preventing rotation of the rotatable paddle 500 aboutthe axis of the valgus portion of the IM rod 10. The securing means 550is preferably self-aligning, such that the surgeon does not have to beconcerned with placing the rotatable paddle 500 in the correctorientation prior to securing the paddle 500 in place. In the embodimentshown in FIG. 21, the locking means includes a generally L-shapedlocking member 550. A proximal end of the locking member 550 is providedwith an upwardly extending stop member 552. The locking member 550 isconfigured to selectively lodge the stop member 552 in the IM rodaperture 510. The locking member 550 is pivotally mounted to the paddle500, such as via a cross-pin 561. The locking member 550 is preferablynormally biased into an open position, such as by a captured spring 554.Turning down a buttress screw 556 forces the locking member 550 to pivotthe stop member 552 into the IM rod aperture 510 and into contact with aposterior side of the IM rod 10. The stop member 552 abuts against aflat portion of the IM rod 10, which serves to selectively lock therotatable paddle 500 in a non-rotational relationship with the IM rod10. The stop member 552 also prevents translation or sliding of therotatable distal IM paddle 500 along the valgus portion of the IM rod10. When the surgeon is finished using the distal IM paddle 500, thepaddle 500 is removed simply by reversing the buttress screw, whichallows the stop member 550 to pivot out of the IM rod aperture 510.

FIG. 24 shows a re-cut guide 680 that can be readily pinned to the femurfor use in making a distal re-cut (FIG. 14) or an anterior re-cut (FIG.15). The re-cut guide 680 features a relatively large, flat paddle witha central cutout. The central cutout assists in maneuvering the recutguide 680 under MIS conditions. The large flat surface allows foraccurate placement of the recut guide 680 against the flat of ananterior or distal cut femur. An abutment shoulder along the proximalface of the guide 680 matches the right angle formed between theanterior and distal cut surfaces, which further assists in accurateplacement of the guide 680 on the femur. The recut guide 680 ispreferably provided with divergent pin bores, which serve to provide amore secure attachment of the recut guide 680 to the femur.

FIG. 26 shows an alternative embodiment of an ARC femoral resectionblock 700 that is downsized and configured for use in an MIS medialapproach. The 4-in-1 cut block of FIG. 26 is not universal. The blockshown in FIG. 26 is for a left knee. The lateral side of the resectionblock 700, which is the right side of the block in FIG. 26, is downsizedrelative to the medial side, since there is less space available on thelateral size when using a medial, quad sparing approach. A pin outrigger705, preferably having an offset through bore, is preferably providedalong the medial side of the block 700. The foregoing features would bereversed for a right knee femoral resection block 700. For addedstability, the resection block 700 can also be provided with secondaryfixation holes 710 through the face of the block 700. Overall, the cutblock features a thin side profile for MIS procedures.

FIG. 29 shows a preferred embodiment of a two arm alignment guide 740that is configured particularly for use in a medially oriented MISincision. The alignment guide 740 has an IM rod holder portion 741having an IM rod aperture 742 therethrough. A horizontal arm 743 extendsfrom one side of the IM rod holder portion 741. A vertical arm 744extends from an adjacent side of the IM rod holder portion 741. Thehorizontal arm 743 is located along a curved portion of the IM rodaperture 742, while the vertical arm 744 is located along a flat portionof the IM rod aperture. The vertical arm 744 is threaded into the IM rodholder portion 741, and is configured for use in securing the alignmentguide 740 on the IM rod 10, i.e. by a leading end of the vertical armthreading against the flat of the IM rod 10. The side and vertical arms743, 744 are set at a right angle relative to one another. In use, thesurgeon slides the alignment guide 740 into the incision with thehorizontal arm 743 oriented generally medially and the vertical arm 744oriented generally anteriorly. Unlike prior art alignment guides, thetwo arm alignment guide 740 does not have protruding structures on theposterior and lateral sides, which makes it easier to position thealignment guide 740 on the IM rod when operating in MIS conditions. Thesurgeon slides the IM rod aperture 742 onto the valgus portion of the IMrod 10, preferably until the IM rod holder portion abuts against a stopmember 19 on the IM rod 10. The surgeon secures the alignment guide ontothe rod by threading down the vertical arm 744 until a leading end ofthe vertical arm 744 abuts against the anterior flat surface of the IMrod 10. The surgeon aligns the vertical arm 744 with the trochleargroove (A/P axis). The horizontal arm 743 can optionally be used toreference the medial epicondyle as a secondary landmark. When thevertical arm 744 is aligned with the trochlear groove and the surgeon issatisfied with the alignment, the IM rod 10 is impacted until the finsof the rod are no longer visible. The components of the two armalignment guide 740 are minimized in size for use in MIS procedures. Thetwo arm alignment guide 740 is preferably configured as a universalalignment guide, i.e. it can be used on a right or a left knee simply byflipping the guide 740. The embodiment shown in FIG. 29 is configuredfor use on an IM rod in which the flats of the rod are positionedanteriorly and posteriorly (A-P). If used with an IM rod in which theflats are positioned medially and laterally (M-L), the vertical arm 744would be positioned over a curved portion of the IM rod aperture 742,while the horizontal arm 743 would be positioned along a flat portion ofthe IM rod aperture 742 and would be configured to thread against theflat. The horizontal arm 743 is preferably formed integrally with the IMrod holder portion 741. Alternatively, the horizontal arm 743 can threadinto the holder portion 741, and can be configured for use in securingthe alignment guide 740 to the IM rod 10. If both arms 743, 744 threadinto the IM rod holder portion 741, then the alignment guide 740 can beused with either an A-P or M-L oriented IM rod. Additionally, the IM rodaperture 742 can be annular, so as to provide a rotatable featuresimilar to that of the rotatable paddle described herein, with one orboth arms 743, 744 configured to thread down to the flat of the IM rod10 to prevent rotation. The vertical arm 744 could be configured topivot medially for insertion in MIS incisions, with a lower portion ofthe vertical arm 744 configured to abut against the flat of the IM rodwhen pivoted to a vertical position.

FIGS. 68-70 shows views of a distal IM rod paddle 500 and an insertportion 580. The embodiments of FIGS. 68-70 are particularly suited formaking distal cuts, such as in a distal cut first procedure. The insertportion 580 has an upper bar 582 and downwardly depending legs 586, withthe legs 586 ending in lateral feet or paddles 588. The upper bar 582has a slot or window 583 for receiving a stylus or pin for use insetting a reference point on an anterior or high point of the femur.Each of the lateral feet 588 has a hole 589 for use in establishing areference point on the femur. The holes 589 are positioned to match pegson proximal face of a femoral cut block. The distal IM paddle 500 shownin FIGS. 68-70 is similar to the paddle 500 shown in FIG. 20. However,the paddle legs 506 of the distal IM paddle 500 are provided with alengthwise slot 507. When the insert portion 580 is inserted into thedistal IM paddle 500, the holes 589 of the insert portion 580 arepositioned in the lengthwise slot 507, which allows the surgeon to drillthrough the hole 589 and slot 507 and into the distal face of the femurto form the reference holes. The insert portion 580 is then removed. Adistal cut is made, such as by using the modular quick connector 640 andthe distal resection guide 660. After the distal resection, the pegs ofa femoral cut block are inserted into the reference holes. The femoralresection block is secured to the distal cut femur, and the box cuts arethen made.

Modular Universal Caliper

FIGS. 31-37 provides views of a preferred embodiment of a modularuniversal sizing caliper 140. As shown in FIGS. 31-37, the caliper 140includes a sizer portion 130, a reference portion 121, and a stylusholder 101 on an anterior end of the sizer portion 130. The referenceportion 121 is slidably engaged to the sizer portion 130. As will bedescribed in further detail below, the reference portion 121 can beseparated from the sizer portion 130 by pulling the reference portion121 upward relative to the sizer portion 130. The reference portion 121can then be rotated 180 degrees about its vertical axis and top-loadedback onto the sizer portion 130. As will be described below, thisfeature contributes to the use of the caliper on either a left or rightknee.

The sizer portion 130 has a pair of vertical bar portions 135A, 135B.The vertical bar portions 135A, 135B are joined or fixed to one anotherin a substantially parallel and spaced apart relationship, such as by across-bar 137. Anterior portions of the vertical bar portions 135A, 135Bare unimpeded so as to provide a sliding engagement with the referenceportion 121. The unimpeded anterior bar portions are of sufficientlength to allow for sizing over a selected range of anatomical variation(e.g. from sizes 1 to 6). A series of calibration marks 139 are formedor imprinted on a posterior side of at least one, and preferably both,of the vertical bar portions 135A, 135B.

The sizer portion 130 includes at least one posterior paddle 136configured to abut against the posterior femoral condyles of a patientduring the sizing procedure. The sizer portion 130 preferably includes apair of posterior paddles 136, as shown in FIGS. 31-53. The posteriorpaddles 136 are spaced apart a distance sufficient to allow one paddle136 to rest on the medial posterior condyle and the other paddle 136 torest on the lateral posterior condyle during sizing of the femur. Theposterior paddles 136 extend distally from the sizer portion 130. Anupper surface of the posterior paddles 136 is preferably a flat planersurface. The posterior paddles 136 are preferably set at an orientationof about 90 degrees relative to the vertical bar portions 135A, 135. Thelower surface of the posterior paddles 136 may be angled or sloped inorder to facilitate placement of the paddles 136 on the posteriorcondyles during an MIS procedure. As shown in FIG. 31-37, the cross-bar137 is elevated above the paddles 136, a feature that provides room forclearance between the cross-bar 137 and the tubercle/intercondylareminence of the tibial plateau.

The reference portion 121 is also provided with features that are usedto set external rotation for a 4-in-1 cut block. As shown in FIGS. 31-37and 48-53, a medial external orientation wing 268M extends from a medialside of the top-loading reference portion 121. A lateral externalorientation wing 268L extends from a lateral side of the top loadingreference portion 121. The medial and lateral external orientation wings268M, 268L are provided with a set of drill holes 263 that match theposition of a pair of fixation holes on a 4-in-1 cut block and whichprovide zero degrees of offset between the reference portion 121 and the4-in-1 cut block. The medial and lateral external orientation wings268M, 268L are provided with a second set of drill holes 263-O that alsomatch the position of the pair of fixation holes on the 4-in-1 cutblock, but which are offset so as to provide a selected degree of offsetbetween the reference portion 121 and the 4-in-1 cut block. The selecteddegree of offset is preferably 3 degrees. The offset holes 263-O areused when external rotation is set based on the posterior condyles. Thezero degree holes 263 are typically used when the surgeon elects tovisually set external rotation, such as in situations where theposterior condyles are worn or otherwise deteriorated. To assist invisually determining the external rotation, an orientation opening 270and associated reference marks 271, 272 can be provided through the body260 of the reference portion. The orientation opening 270 allows thesurgeon to view the underlying distal cut femur, and is preferablypositioned to provide the surgeon with a view of the trochlear groove. Apair of opposing trochlear groove reference marks 271 are provided alonganterior and posterior aspects of the rim of the orientation opening 270for use in making a visual check of the position of the referenceportion 121 relative to the trochlear groove. A pair of opposing M-Lreference marks 272 are provided on medial and lateral aspects of therim of the orientation opening 270 for use in making a visual check ofthe position of the reference portion 121 relative to the medial-lateralorientation, such as when using the zero degree holes 263 or when sizingworn or deteriorated condyles.

Top Loading Caliper

FIGS. 35-40 provides views of a top-loading sizing caliper 140 that isparticularly adapted for use in MIS knee procedures. The top-loadingsizing caliper 140 comprises three separable components: a paddleportion 200, a sizer portion 130, and a reference portion 121. Theseparable components 200, 130, 121 allow the top loading caliper 140 tobe used in MIS knee procedures that are performed through a very smallincision.

The paddle portion 200 of the top loading sizing caliper 140 includes abase portion 210 that includes means for selectively engaging the sizerportion 130. In the embodiment shown in FIGS. 35-40, the base portion210 is a generally planar structure that serves to orient and supportthe various functional components of the paddle portion 210 in a fixedorientation.

A proximal side of the base portion 210 includes means for selectivelyengaging the sizer portion 130. In the embodiment shown in FIGS. 35-40,the means is a shaft 205 and a pair of pegs 209. The shaft 205 extendsfrom the proximal side of the base portion 210 adjacent an anterior endof the base portion 210. The shaft 209 includes a groove 206, which ispreferably annular and which is sized and positioned to selectivelyengage a spring plunger on the sizer portion 130. The shaft 205 is sizedto closely match a bore on the sizer portion 130. The pegs 209 extendfrom the proximal side of the base portion 210. The pegs 209 arepreferably positioned below the shaft 205. The shaft 205 and pegs 209are spaced apart from one another in a substantially parallelorientation, and extend substantially perpendicularly from the baseportion 210. The generally triangular orientation of the shaft 205 andpegs 209 shown in FIGS. 35-40 prevents rotational movement between thesizer portion 130 and the paddle portion 200. The shaft 205 and pegs 209are preferably round, but they could have other configurations, such assquare or keyed. While other types of engagement means could be used(e.g. screws; bores keyed to pegs on the sizer portion 130; quickconnect couplings; square drives), the embodiment shown in FIGS. 35-40is simple to use and provides sufficient engagement between the sizerportion 130 and the paddle 200.

In a preferred embodiment, a handle portion 240 extends from the distalside of the base portion 210, preferably in a substantiallyperpendicular orientation. As indicated in FIGS. 35-40, the handleportion 240 can be provided with a textured surface (e.g. plurality ofannular rings; knurls; grooves; cross-hatching) to assist the surgeon ingripping the handle portion 240. The handle portion 240 assists thesurgeon in affixing the paddle portion 200 to the sizer portion 130,inserting the paddle-sizer portion complex 200, 130 through theincision, positioning the posterior paddles 236 against the posteriorfemoral condyles, holding the paddle-sizer portion complex 200, 130during fixation of the sizer portion 130 to the distal cut femur, and inseparating the paddle portion 200 from the fixed sizer portion 130. Forease of manufacture, the handle portion 240 and the engagement shaft 209can be machined as a single component, with a threaded portion formedbetween the handle portion 240 and the engagement shaft 209 for use inthreading the component into a threaded receiving bore in the baseportion 210 of the paddle portion 200. Alternatively, the threadedportion can be eliminated, and the handle portion 240 can be pinned orotherwise fixed in the receiving bore of the base portion 210.

The paddle portion 130 includes at least one posterior paddle 236positioned and configured to abut against the posterior femoral condylesduring the sizing procedure. The sizer portion 130 preferably includes apair of posterior paddles 236, as shown in FIGS. 41-43. The posteriorpaddles 236 preferably have the characteristics described above withreference to the universal sizing caliper of FIGS. 31-53. In thepreferred embodiment shown in FIGS. 41-43, each of the posterior paddles236 is joined to a posterior end of the paddle base portion 210 by adistal arm 235. The distal arms 235 are configured to have a minimalprofile while still providing adequate support for the posterior paddles236. As indicated in the side view of FIGS. 41-43, the distal arm 235can be configured to provide an offset between the posterior end of thepaddle base portion 210 and the upper or anterior surface of theposterior paddle 236, which allows for tubercle clearance. Upper oranterior surfaces of the distal arms 235 are preferably flat and aresubstantially level with one another. As indicated in FIGS. 41-53, theflat anterior surface of the distal arms 235 can be configured to abutagainst the distal surface of the sizer portion 130, which providesfurther rotational stability to the paddle-sizer portion 200-130complex. Since rotational stability is secured by the shaft 205 and thedistal arms 235, the pegs 209 could be eliminated from the paddleportion 200.

The base portion 210 is sized and configured to support the functionalcomponents of the paddle portion 200 while also providing a smallprofile that is suitable for use in DCF MIS knee procedures. Withreference to FIGS. 41-43, preferred characteristics of the base portion210 include a posterior portion having a width sufficient to allow theposterior paddles 236 to abut against the medial and lateral posteriorcondyles, a central portion of sufficient width to support and space thepegs 209, and an anterior region that closely encircles the shaft 205.

As shown in FIGS. 44-47 and 54-57, the sizer portion 130 of thetop-loading sizing caliper 140 has a pair of vertical bar portions 135A,135B. Alternatively, the sizer portion 130 could have one bar or aplurality of bars 135. As shown in FIGS. 44-47 and 54-70, the verticalbar portions 135A, 135B are joined or fixed to one another in asubstantially parallel and spaced apart relationship, such as by across-bar 137. Anterior portions of the vertical bar portions 135A, 135Bare unimpeded so as to provide a sliding engagement with the referenceportion 121. The unimpeded anterior bar portions 135A, 135B are ofsufficient length to allow for sizing over a selected range ofanatomical variation (e.g. from sizes 1 to 6). The vertical bar portions135A, 135B can be provided with a ball plunger 142, which serves to abutagainst the reference portion 121 and thereby provide some resistance tosliding between the sizer portion 130 and the reference portion 121. Aseries of calibration marks 139 (e.g. bars; or bars and associated sizenumbers) are formed, laser marked or otherwise imprinted on a posteriorside of at least one, and preferably both, of the vertical bar portions135A, 135B.

Unlike the sizer portion 130 shown in FIGS. 31-53, the top-loading sizerportion 130 does not include posterior paddles 136, since the paddlesare provided by the separate paddle portion 200 described above. Thetop-loading sizer portion 130 instead has means for selectivelyattaching the top-loading sizer 130 portion to the paddle portion 200.In the embodiment shown in FIGS. 39-40 and 59, the means includes pegbores 149 sized to closely receive the pegs 209 of the paddle portion200, as well as a shaft bore 145 sized to closely receive the shaft 205of the paddle portion 200. As shown in the top view of FIGS. 44-47 and54-57, the crossbar 137 includes a proximal indent 141 that is sized toreceive at least a portion of the base portion 210. As shown in FIGS.35-40, with the base portion 210 lodged in the proximal indent 141 ofthe sizer portion 130, the anterior surfaces of the distal arms 235preferably abut against the posterior surface of the crossbar 137, whichprovides additional stability to the paddle-sizer portion complex 200,130. Additionally, the proximal indent contributes to the minimalprofile of the paddle-sizer portion complex 200, 130, and thuscontributes to its use in MIS procedures.

As shown in FIGS. 44-47 and 54-57, the sizer portion 130 includesfixation wings 138A, 138B, which preferably extend from opposing sidesof the sizer portion 130. The fixation wings 138A, 138B are preferablypositioned along or adjacent the posterior end of the sizer portion 130.In the embodiment of FIGS. 44-47 and 54-57, the fixation wings 138A,138B are formed as extension portions of the cross bar 137. Each of thefixation wings 138A, 138B is provided with at least one fixation bore143A, 143S for use in affixing the sizer portion 130 to the distal cutfemur. In the embodiment shown in FIGS. 44-47 and 54-57, each fixationwing 138A, 138B is provided with two fixation bores. One of the bores,which is preferably positioned medially, is a straight bore 1435. Theother bore, which is preferably positioned laterally, is an angled bore143A. The angled bores 143A preferably angle inward (varus) relative tothe midline of the femur. This configuration provides the surgeon withseveral options for fixing the sizer portion 130 to the distal cutfemur, which may prove useful when operating under MIS conditions. Forexample, when working from a medial or anterior medial approach throughan MIS incision, the surgeon may find it preferable, due to the limitedamount of space, to insert a first pin in the medial angled bore 143Aand a second pin in the lateral straight bore 1435. Depending onoperating conditions, the surgeon could choose other combinations, suchas the two straight bores 143S, two angled bore 143A, three bores, fourbores etc.

Once the sizer portion 130 has been pinned to the distal cut femur, thesurgeon can remove the paddle portion 200 from the sizer portion 130 bypulling the paddle portion 200 away from the distal femur. This leavesthe sizer portion 130 properly positioned on the distal femur. In mostcircumstances, the sizer portion 130 will be pinned with the top-loadingreference portion 121 already in place. However, sizer portion 130 couldbe pinned without the top-loading reference portion 121 in place. In asubsequent step, the top-loading reference portion 121 would then beplaced in the incision and top-loaded onto the vertical bar portions135A, 135B of the sizer portion 130. A stylus 100 is inserted in thestylus holder 101 of the reference portion 121. The sizer-referenceportion complex 130, 121 is then used to determine the size of thefemur.

As shown in FIGS. 48-50, the reference portion 121 is preferably agenerally planar body 260 having a pair of generally vertical tracks265A, 265B formed therein. The tracks 265A, 265B are sized andpositioned to slidably engage the vertical bar portions 135A, 135B ofthe sizer portion 130. The tracks 135A, 135B are preferably enclosedalong most of their length by the body 260 of the reference portion 121.The tracks 265A, 265B and associated bars 135A, 135B could be anyconfiguration (e.g. square, round, hex). The body 260 is preferablyprovided with at least one and preferably two reference windows 269A,269B. Each of the reference windows 269A, 269B communicates with a track265A, 265B, such that calibration marks 139 on the vertical bar portions135A, 135B of the sizer portion 130 are visible through the referencewindow 269A, 269B. As shown in FIGS. 58B and 61A, a reference mark 129is formed or imprinted on the body 260 adjacent the reference window265, such that the position of the reference mark 129 can be readrelative to the calibration marks 139 on the bars 135A, 135B of thesizer portion 130. Reference windows 269A, 269B are preferably providedon opposing faces of the reference portion body 260, which allows thereference bar 121 to be flipped 180 degrees for use in sizing either aleft or a right knee.

The top-loading reference portion 121 is also provided with featuresthat are used to set external rotation for a 4-in-1 cut block. A medialexternal orientation wing 268M extends from a medial side of thetop-loading reference portion 121. A lateral external orientation wing268L extends from a lateral side of the top loading reference portion121. The medial and lateral external orientation wings 268M, 268L areprovided with a set of drill holes 263 that match the position of a pairof fixation holes on a 4-in-1 cut block and which provide zero degreesof offset between the reference portion 121 and the 4-in-1 cut block.The medial and lateral external orientation wings 268M, 268L areprovided with a second set of drill holes 263-O that also match theposition of the pair of fixation holes on the 4-in-1 cut block, butwhich are offset so as to provide a selected degree of offset betweenthe reference portion 121 and the 4-in-1 cut block. The selected degreeof offset is preferably 3 degrees. The three degree holes 263-O are usedwhen external rotation is set based on the posterior condyles. The zerodegree holes 263 are typically used when the surgeon elects to visuallyset external rotation, such as in situations where the posteriorcondyles are worn or otherwise deteriorated. To assist in visuallydetermining the external rotation, an orientation opening 270 andassociated reference marks 271, 272 can be provided through the body 260of the top-loading reference portion. The orientation opening 270 allowsthe surgeon to view the underlying distal cut femur, and is preferablypositioned to provide the surgeon with a view of the trochlear groove. Apair of opposing trochlear groove reference marks 271 are provided alonganterior and posterior aspects of the rim of the orientation opening 270for use in making a visual check of the position of the referenceportion 121 relative to the trochlear groove. A pair of opposing M-Lreference marks 272 are provided on medial and lateral aspects of therim of the orientation opening 270 for use in making a visual check ofthe position of the reference portion 121 relative to the medial-lateralorientation, such as when using the zero degree holes 263 or when sizingworn or deteriorated condyles.

Means are also provided for attaching a stylus holder 101 to thereference portion 121, preferably in a rotatable relationship. In theembodiment shown in FIGS. 35-62, the means includes an anterior bore 275sized to receive a lower end of a stylus holder 101. The lower end ofthe stylus holder 101 includes an annular groove 103. The body 260 ofthe reference portion 121 has a set pin bore 276. The set pin bore 276is positioned to receive a set pin such that the pin engages the annulargroove 103 of the stylus holder 101, thus retaining the stylus holder101 on the reference portion 121 while allowing the stylus holder 101 torotate relative to the reference portion 121.

Front and Top Loading Caliper

FIGS. 51-57 provides views of a front and top-loading caliper 140 thatis particularly adapted for use in MIS knee procedures. The front andtop-loading caliper 140 includes many of the features of the top loadingcaliper 140 described above, but has the added benefit of allowing thereference portion 121 to be loaded onto the sizer portion 130 from thefront. The front and top-loading sizing caliper 140 comprises threeseparable components: a paddle portion 200, a sizer portion 130, and areference portion 121. As will be described in further detail below,sequential use of the three components 200, 130, 121 allows the toploading caliper 140 to be used in MIS knee procedures that are performedthrough a very small incision. In the limited space available in MISknee procedures, front loading can confer a significant advantage.

As indicated in FIGS. 51-57, the paddle portion 200 described above ispreferably used as the paddle portion 200 of the front loading caliper140. As shown particularly in FIGS. 51-53, the sizer portion 130 of thefront loading caliper 140 is similar to that of the sizer portion 130that is used with the top loading caliper, but additionally has featuresthat enable front-loading (compare FIGS. 44-47 and 54-57). As shown inFIGS. 44-47 and 51-57, the sizer portion 130 of the front-loading sizingcaliper 140 has a pair of vertical bar portions 135A, 135B. As shown inFIGS. 44-47 and 54-57, the vertical bar portions 135A, 135B are joinedor fixed to one another in a substantially parallel and spaced apartrelationship, such as by a cross-bar 137. Anterior portions of thevertical bar portions 135A, 135B are unimpeded so as to provide asliding engagement with the reference portion 121. The unimpededanterior bar portions 135A, 135B are of sufficient length to allow forsizing over a selected range of anatomical variation (e.g. from sizes 1to 6). A series of calibration marks 139 (e.g. cross-hatches; orcross-hatches and associated size numbers) are formed or imprinted on aposterior side of at least one, and preferably both, of the vertical barportions 135A, 135B.

To enable front loading, a generally L-shaped track 131 is provided onan outer side of each of the vertical bar portions 135A, 135B of thesizer portion 130. As shown in the side view of FIGS. 44-47 and 54-57,the L-shaped track 131 includes a substantially vertical lengthwiseportion and a posterior portion 131P that opens on the distal side ofthe sizer portion 130. A distal end of the posterior portion 131P of theL-shaped track 131 provides a front-load opening 132 for use in frontloading a reference portion 121 onto the sizer portion 130. Turning nowto FIGS. 60-62, it can be seen that the reference portion 121 of the toploading caliper 140 is provided with a pair of tracks 265A, 265B. Thetracks 265A, 265B are in the form of lengthwise slots formed in the body260 of the reference portion 121. A tab 266A, 266B is provided adjacenta posterior end of each track 265A, 265B. The tabs 266A, 266B are sizedsuch that the A-P dimension of the tabs 266A, 266B can pass through thefront-load opening 132 of the sizer portion 130. The tabs 266A, 266B arealso sized such that they closely fit the width of the vertical portionof the L-shaped slot 131, which prevents the reference portion 121 fromwobbling unduly in the sizer portion 130. Alternatively, the mechanismcould be reversed, such that the slot 131 resides in the referenceportion 121 and the tabs 266 are located on the bars 135A, 135B of thesizer portion 130. In another embodiment, the slot 131 and tabs 266 canbe eliminated and the vertical bars 135A, 135B can reside without distalrestraint within the tracks 265A, 265B of the reference portion 121.

Once the sizer portion 130 has been pinned to the distal cut femur, thesurgeon removes the paddle portion 200 from the sizer portion 130 bypulling the paddle portion 200 away from the distal femur. This leavesthe sizer portion 130 properly positioned on the distal femur. Thefront-loading reference portion 121 is then placed in the incision andfront-loaded onto the vertical bar portions 135A, 135B of the sizerportion 130. A stylus 100 is inserted in the stylus holder 101 of thereference portion 121. The sizer-reference portion complex 130, 121 isthen used to determine the size of the femur.

The embodiment shown in FIGS. 51-57 also includes features that allowthe caliper to be loaded from the top, such that the caliper of FIGS.51-57 can function as both a front and top loading caliper. For example,the anterior portion of the L-shaped slot 131 can communicate with thetop or anterior end of the sizer portion 130 such that the tabs 266A,266B can be inserted into the L-shaped slot 131 from the top.

The foregoing modular calipers provide various advantages, many of whichfacilitate the ease and accuracy of MIS procedures. Multi-piece optionsallow the surgeon to use the calipers in multiple ways, depending onsurgeon preference, such as: (1) the surgeon can insert the caliper withthe paddles but without the stylus; (2) once the caliper is positioned,it can be pinned in place and the paddle portion can be removed; (3) thestylus can be inserted into the caliper for use in sizing and to adjustcorrect A-P positioning; (4) once external rotation is set, pin holescan be drilled for accurate placement of a 4-in-1 block. The modularcalipers 140 can used as traditional one piece caliper or in a modularfashion, depending on surgeon preference. The calipers 140 areconfigured to allow for better visualization of landmarks during use,particularly under MIS conditions. The surgeon can add parts as neededor remove parts to optimize visualization. The modular design allows thesurgeon to manipulate leg position (flexion/extension) during sizing,A-P positioning, rotations, etc. The calipers allow for one paddle body200 that can be used with various caliper configurations. The universalfeatures described herein allow the same caliper to be used for left orright sizing, which reduces instrument inventory. However, the caliperdoes not have to be left-right; all of the advantages can be providedwith separate, dedicated left and right versions of the calipers.

When operating under MIS conditions, it can be difficult to insert astylus through the MIS incision and into the sizing caliper. To addressthis problem, the sizing calipers disclosed herein include features thatallow the stylus to be loaded from the side, such as through ananterior-medial incision of minimal length. FIGS. 63-64 provide views ofpreferred embodiments of a side loading stylus 100 that is particularlyadapted for MIS procedures using the modular sizing calipers 140described herein. The side-loading stylus 100 is configured for use witha side-loading stylus holder of the type shown for example in FIGS.35-62 show a side-loading stylus 100 loaded into a side-loading stylusholder 101. The stylus bore 102 of the side-loading stylus holder 101 isprovided with a side-loading aperture, which allows the side-loadingstylus 100 to be slide through the side-loading aperture and intoengagement with the stylus bore 102. To facilitate MIS procedures, thestylus holder 101 is preferably rotatable relative to the sizer portion130, such that the surgeon can rotate the side-loading aperture to asuitable position for receipt of the side-loading stylus 101. Anteriorand posterior inner walls of the side-loading stylus bore 102 are flat.A ball-plunger or other selective engagement means is positioned alongthe posterior wall of the stylus bore 102 for selectively engaging aposterior surface of the side-loading stylus 100. The side-loadingstylus 100 includes a central engagement portion that has flat anteriorand posterior surfaces. The flat A-P surfaces of the side-loading stylus100 are spaced apart such that they closely pass through theside-loading aperture of the stylus holder 101 and substantially intoabutment with the flat A-P inner walls of the stylus bore 102. The flatabutting surfaces of the stylus bore 102 and the side-loading stylus 100allow the stylus 100 to translate or slide within the stylus bore 102,and also serve to generally retard A-P rotation of the stylus 100relative to the caliper 140.

The side-loading stylus 100 and the stylus bore 102 include means forselective engagement. In the embodiment shown in FIG. 63, a posteriorsurface of the central engaging portion of the side-loading stylusincludes a series of holes that are sized to receive a ball-plungerlocated in the distal wall of the stylus bore 102. In the embodimentshown in FIG. 63, the holes are positioned in a lengthwise groove ortrack, which serves to better engage the ball plunger. The engagementbetween the side-loading stylus 100 and the stylus bore 102 ispreferably relatively weak, such that the surgeon can slide theside-loading stylus 100 proximally and distally without undue effort,yet the stylus 100 will not inadvertently slide proximally or distally.

A posterior surface of the central engagement portion of theside-loading stylus 100 is preferably provided with size markers (e.g.bars, or bars and associated size numbers). The sizer markers arepositioned such that a reading can be made of the size of the femur.

FIG. 63 shows a side loading stylus 100 that has a ski tip, while FIG.64 shows a side-loading stylus 100 that has a ball tip. As shown inFIGS. 63 and 66, the side loading stylus 100 is preferably provided witha flattened tab handle for use in sliding the stylus proximally anddistally within an MIS incision. The tab handle includes A-P proximalprotrusions for use in pushing the stylus 100 proximally, as well as A-Pdistal protrusions for use in pulling the stylus 100 distally.

In the discussion of sizing calipers herein, anatomical referencescorrespond to orientation of the caliper when positioned on a distal endof a femur. As used herein, “sizer portion” 130 refers generally to theportion of the caliper that includes a series of calibration markings139 and which remains generally stationary during the sizing procedure.“Reference portion” 121 refers generally to the portion of the caliper140 that includes a reference mark 129 and which translates up and downrelative to the sizer portion 130 during the sizing procedure.

Although the present invention has been described in terms of specificembodiments, it is anticipated that alterations and modificationsthereof will no doubt become apparent to those skilled in the art. It istherefore intended that the following claims be interpreted as coveringall alterations and modifications that fall within the true spirit andscope of the invention.

What is claimed is:
 1. An anti-backout stylus instrument assemblycomprising: a stylus configured for insertion into a locking stylusholder, a locking stylus holder, said locking stylus holder configuredto engage said stylus at a series of discrete positions during insertionof said stylus into said locking stylus holder, and to prevent saidstylus from being withdrawn to a previous one of said discrete positionsto thereby prevent inadvertent backing out of said stylus from saidlocking stylus holder, wherein each of said discrete positions matches aparticular femoral size, such that each engagement of one of saiddiscrete positions by said locking stylus holder indicates a femoralsize, wherein each engagement of one of said discrete positions by saidlocking stylus holder produces a sound, said sound providing indicationof a femoral size.
 2. The instrument assembly of claim 1, furthercomprising a disengagement member on said locking stylus holder, saiddisengagement member configured to selectively disengage said lockingstylus holder from said stylus and to thereby allow said stylus to bewithdrawn through said stylus holder.
 3. The instrument assembly ofclaim 2, wherein said disengagement member comprises a part of saidstylus bore of said locking stylus holder being formed by a biasedbutton, said biased button configured such that a user can selectivelybackout said stylus from said locking stylus holder by depressing saidbiased button and simultaneously pulling said stylus rearward.
 4. Theinstrument assembly of claim 3, wherein said biased button has a stopmember on a lower interior wall, said biased button normally biasedupward such that said stop member is positioned to engage one of aseries of detents formed along a lower surface of an engagement portionof said stylus.
 5. The instrument assembly of claim 4, wherein saidbiased button is biased by a captured spring.
 6. The instrument assemblyof claim 1, further comprising femoral size markings on said stylus foruse in visually determining a femoral size.
 7. An anti-backout stylusinstrument assembly comprising: a locking stylus holder on a supportmembers, said locking stylus holder having a stylus bore for receiving astylus, said stylus bore having a stop member disposed therein, saidstop member biased to normally engage a detent of a stylus disposed insaid stylus bore, a stylus, said stylus having substantially flatportion, a tip on a forward end, and a sloped portion between said flatportion and said tip, a lower side of said flat portion of said stylushaving a series of detents thereon, said detents configured to depressand pass over said stop member when said stylus is slid forward intosaid stylus bore, but to engage said stop member when said stylus isslid distally to thereby prevent inadvertent withdrawal of said stylusfrom said stylus bore, wherein each of said detents is positioned tomatch a particular femoral size, such that each engagement of a detentby said stop member indicates a femoral size, wherein each engagement ofa detent by said stop member produces a sound, said sound providingindication of a femoral size.
 8. The instrument assembly of claim 7,wherein each of said detents has an inclined forward side configured toslide over said stop member when said stylus is slid forward and asubstantially flat or declined trailing side configured to abut againstsaid stop member when said stylus is slid backward.
 9. The instrumentassembly of claim 8, wherein a part of said stylus bore of said lockingstylus holder is formed by a biased button, such that a user canselectively backout said stylus by depressing said biased button andsimultaneously pulling said stylus distally.
 10. The instrument assemblyof claim 9, wherein said biased button comprises a bore for receivingsaid anti-back out stylus, said stop member on a lower wall of saidbiased button bore, said biased button normally biased anteriorly suchthat said stop member normally engages said detents formed along aposterior surface of an engagement portion of said stylus.
 11. Theinstrument assembly of claim 10, wherein said biased button is biased bya captured spring.
 12. The instrument assembly of claim 7, wherein saidsupport member is an anterior rough cut guide having an anteriorresection slot therethrough.
 13. The instrument assembly of claim 12,wherein said anterior rough cut guide is configured to insert into adistal intramedullary paddle mounted on an intramedullary rod.
 14. Theinstrument assembly of claim 13, wherein said support member isconfigured to insert into said distal intramedullary paddle via a pairof support bars depending downward from said anterior rough cut guide.15. The instrument assembly of claim 7, further comprising femoral sizemarkings on said stylus for use in visually determining a femoral size.